Everything Johnny said is good I have a couple to add
2. Don't let any tell you "You're doing it wrong" I don't mean to ignore advice but who said there's a right way to do something?
That is a great video, thanks.
Lots of great musicians and teachers, many of them here on UU say there are some rules worth following. While there are many parallels with spoken language, there are a few rules, that if broken, will make learning to play and/or progressing more difficult. Some will get frustrated and quit if they can't figure it out on their own. Some people pickup an instrument and instinctively learn to play it by ear. Even BB King didn't learn chords until his 40's, so there is a lot to this theory, but ultimately, BB did follow a few rules and learn his chords and was able to name the notes he was playing so that he could "play well with others." I have found it difficult to learn music theory and certain playing skills and have benefited from following a few rational "rules." If they help me, great. If someone else doesn't need'em to learn, great. I'm old now, and always and never are words I heed with caution. I do agree with not letting "rules" ruin your creativity. It's just in the degree. I think that between the creativity and the discipline extremes, there is a happy medium for all. As in politics, some will lean more towards the left and some more towards the right. Have fun and play the hell out of that uke.